Multilayered capacitor

ABSTRACT

A multilayered capacitor includes a capacitor body including a plurality of dielectric layers and a plurality of internal electrodes; and external electrodes disposed on both end portions of the capacitor body and connected to exposed portions of the internal electrodes, respectively. Each of the external electrodes includes a conductive layer formed on the capacitor body and connected to the internal electrodes; an inner plated layer including nickel (Ni) and phosphorus (P), and covering the conductive layer; and an outer plated layer including palladium (Pd) and phosphorus (P), and covering the inner plated layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to Korean Patent ApplicationNo. 10-2019-0034920 filed on Mar. 27, 2019, and Korean PatentApplication No. 10-2019-0054166 filed on May 9, 2019 in the KoreanIntellectual Property Office, the disclosures of which are incorporatedherein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a multilayered capacitor.

BACKGROUND

In a typical multilayered capacitor, a plated layer of an externalelectrode may be formed of a nickel plated layer and a tin plated layer,and may use a tin-containing solder (Sn-based solder) in a case of beingmounted on a substrate.

In the case of tin-containing solder, problems such as cracks may occurwhen a reliability at a temperature of 150° C. or higher is required ina product. In recent years, there has been a tendency to use aconductive adhesive mainly containing epoxy and metallic filler, or thelike, as a bonding material.

However, when the above-mentioned conductive adhesive is used as thebonding material, and the plated layer of the external electrode is madeof tin, a bonding force between the conductive adhesive and the platedlayer may be lowered, which may cause a problem of increasing a mountingfailure of the multilayered capacitor.

SUMMARY

An aspect of the present disclosure is to provide a multilayeredcapacitor capable of preventing a decrease in bonding force between aconductive adhesive and a plated layer to prevent a mounting failure,even when high reliability is required in a case in which themultilayered capacitor is mounted on a substrate using a conductiveadhesive.

According to an aspect of the present disclosure, a multilayeredcapacitor includes a capacitor body including a dielectric layer and aplurality of internal electrodes; and a plurality of external electrodesdisposed on both end portions of the capacitor body and connected toexposed portions of the internal electrodes. Each of the externalelectrodes includes a conductive layer disposed on the capacitor bodyand connected to the internal electrodes; an inner plated layerincluding nickel (Ni) and phosphorus (P), and covering the conductivelayer; and an outer plated layer including palladium (Pd) and phosphorus(P), and covering the inner plated layer.

In an embodiment of the present disclosure, the inner plated layer mayhave a phosphorus content of more than 4% by weight and 8% by weight orless, based on a total weight of the inner plated layer.

In an embodiment of the present disclosure, the inner plated layer maymainly contain nickel (Ni) and include phosphorus (P) as an impuritydispersed in the inner plated layer.

In an embodiment of the present disclosure, the capacitor body mayinclude first and second surfaces facing each other, third and fourthsurfaces connected to the first and second surfaces and facing eachother, and fifth and sixth surfaces connected to the first and secondsurfaces and connected to the third and fourth surfaces, and may includethe plurality of internal electrodes alternately exposed through thethird and fourth surfaces of the capacitor body with the dielectriclayer interposed therebetween.

In an embodiment of the present disclosure, the conductive layer of theexternal electrodes may include connection portions respectivelydisposed on the third and fourth surfaces of the capacitor body andconnected to the exposed portions of the internal electrodes, and bentportions extending from the connection portions to a portion of thefirst surface of the capacitor body.

In an embodiment of the present disclosure, the inner plated layer maybe formed by plating a first metal layer including nickel and phosphoruson the conductive layer by an electroless plating process, and the outerplated layer may be formed by plating a second metal layer includingpalladium and phosphorus on the inner plated layer by an electrolessplating process.

In an embodiment of the present disclosure, the conductive layer mayinclude at least one of copper and silver.

In an embodiment of the present disclosure, the inner plated layer mayhave a thickness of 1 μm to 10 μm.

In an embodiment of the present disclosure, a thickness of the innerplated layer may be greater than a thickness of the outer plated layer.

In an embodiment of the present disclosure, the outer plated layer mayhave a phosphorus content of 2% by weight or more and 6% by weight orless, based on a total weight of the outer plated layer.

In an embodiment of the present disclosure, the outer plated layer maymainly contain palladium (Ni) and include phosphorus (P) as an impuritydispersed in the outer plated layer.

In an embodiment of the present disclosure, each of the externalelectrodes may not contain a tin (Sn) layer.

According to an aspect of the present disclosure, a multilayeredcapacitor includes a capacitor body including a plurality of dielectriclayers and a plurality of internal electrodes; and external electrodesdisposed on both end portions of the capacitor body and connected toexposed portions of the internal electrodes, respectively. Each of theexternal electrodes includes: a conductive layer disposed on thecapacitor body and connected to the internal electrodes; an inner nickel(Ni) layer with phosphorus (P) dispersed therein as an impurity, andcovering the conductive layer; and an outer noble metal layer withphosphorus (P) dispersed therein as an impurity and covering layer theconductive layer.

In an embodiment of the present disclosure, the outer noble metal layermay be a palladium (Pd) layer with phosphorus (P) dispersed therein asthe impurity.

In an embodiment of the present disclosure, the inner nickel (Ni) layermay have a phosphorus content of more than 4% by weight and 8% by weightor less, based on a total weight of the inner nickel layer.

In an embodiment of the present disclosure, the outer noble metal layermay have a phosphorus content of 2% by weight or more and 6% by weightor less, based on a total weight of the outer noble metal layer.

In an embodiment of the present disclosure, a thickness of the innernickel (Ni) layer may be greater than a thickness of the outer noblemetal layer.

In an embodiment of the present disclosure, each of the externalelectrodes may not contain a tin (Sn) layer.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a perspective view schematically illustrating a multilayeredcapacitor according to an embodiment of the present disclosure.

FIGS. 2A and 2B are plan views illustrating first and second internalelectrodes applied to the multilayered capacitor of FIG. 1,respectively.

FIG. 3 is a cross-sectional view taken along line I-I′ in FIG. 1.

FIG. 4 is a cross-sectional view illustrating that only the conductivelayers of the external electrodes in FIG. 3 are formed.

FIG. 5 is a cross-sectional view illustrating that the inner platedlayers are further formed in the external electrodes in FIG. 4.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present disclosure will bedescribed with reference to the accompanying drawings.

However, embodiments of the present disclosure may be modified intovarious other forms, and the scope of the present disclosure is notlimited to the following embodiments.

Further, embodiments of the present disclosure may be provided to morefully explain the present disclosure to those skilled in the art.

Shape and size of elements in drawings may be exaggerated for clarity.

The same reference numerals may be used for the same elements in thesame reference numerals in drawings of respective embodiments.

In addition, ‘including or comprising’ an element throughout thespecification refers to not excluding other elements, but furtherincluding other elements, unless specifically stated otherwise.

Hereinafter, in order to clearly explain embodiments of the presentdisclosure, when directions of a capacitor body 110 are defined, X, Y,and Z refer to a longitudinal direction, a width direction, and athickness direction of the capacitor body 110, respectively. Further, inthis embodiment, the Z direction may be used to have the same concept asa stacking direction in which dielectric layers are stacked.

FIG. 1 is a perspective view schematically illustrating a multilayeredcapacitor according to an embodiment of the present disclosure, FIGS. 2Aand 2B are plan views illustrating first and second internal electrodesapplied to the multilayered capacitor of FIG. 1, respectively, FIG. 3 isa cross-sectional view taken along line I-I′ in FIG. 1, FIG. 4 is across-sectional view illustrating that only the conductive layers of theexternal electrodes in FIG. 3 are formed, and FIG. 5 is across-sectional view illustrating that the inner plated layers arefurther formed in the external electrodes in FIG. 4.

Referring to FIGS. 1 to 5, a multilayered capacitor 100 according to thepresent embodiment may include a capacitor body 110, and first andsecond external electrodes 130 and 140.

The capacitor body 110 may be formed by stacking a plurality ofdielectric layers 111 in a Z direction, and then sintering the stackeddielectric layers 111. In this connection, a boundary between thedielectric layers 111 adjacent to each other in the capacitor body 110may be integrated in a degree that it is difficult to confirm theboundary without using a scanning electron microscope (SEM).

The capacitor body 110 may have a generally hexahedral shape, but thepresent disclosure is not limited thereto. Shape and dimensions of thecapacitor body 110, and the number of stacked layers of the dielectriclayers 111 are not limited to those illustrated in the drawings of thepresent embodiment.

In this embodiment, for convenience of explanation, two surfaces of thecapacitor body 110 facing each other in a Z direction may be defined asfirst and second surfaces 1 and 2, respectively; two surfaces of thecapacitor body 110 connected to the first and second surfaces 1 and 2and facing each other in an X direction may be defined as third andfourth surfaces 3 and 4, respectively; and two surfaces of the capacitorbody 110 connected to the first and second surfaces 1 and 2, connectedto the third and fourth surfaces 3 and 4, and facing each other in an Ydirection may be defined as fifth and sixth surfaces 5 and 6,respectively. Further, in this embodiment, amounting surface of themultilayered capacitor 100 may be the first surface 1 of the capacitorbody 110.

The dielectric layers 111 may include a ceramic material having a highdielectric constant, for example, a barium titanate (BaTiO₃)-based, astrontium titanate (SrTiO₃)-based ceramic powder, or the like, but arenot limited thereto.

Further, a ceramic additive, an organic solvent, a plasticizer, abinder, a dispersant, and the like may be further added to thedielectric layer 111, together with the ceramic powder.

The ceramic additive may be, for example, a transition metal oxide or atransition metal carbide, a rare earth element, magnesium (Mg), aluminum(Al), or the like.

The capacitor body 110 may include an active region serving as a portioncontributing to capacity formation of the capacitor, and upper and lowercovers 112 and 113 formed respectively on upper and lower surfaces ofthe active region in the Z direction as upper and lower margin portions.

The upper and lower covers 112 and 113 may have the same material andconfiguration as the dielectric layer 111, except that they do notinclude internal electrodes.

The upper and lower covers 112 and 113 may be formed by stacking asingle dielectric layer or two or more dielectric layers on upper andlower surfaces of the active region in the Z direction, respectively;and may basically serve to prevent first and second internal electrodes121 and 122 from being damaged by physical or chemical stress.

The first and second internal electrodes 121 and 122 may be electrodesto which different polarities are applied, may be alternately arrangedin the Z direction with the dielectric layer 111 interposedtherebetween, and may be configured such that one end thereof is exposedthrough the third and fourth surfaces 3 and 4 of the capacitor body 110,respectively.

In this case, the first and second internal electrodes 121 and 122 maybe electrically insulated from each other by the dielectric layer 111interposed therebetween.

End portions of the first and second internal electrodes 121 and 122alternately exposed through the third and fourth surfaces 3 and 4 of thecapacitor body 110 may be in contact with and may be electricallyconnected to the first and second external electrodes 130 and 140disposed on the third and fourth surfaces 3 and 4 of the capacitor body110, respectively, to be described later.

In this embodiment, when a predetermined voltage is applied to the firstand second external electrodes 130 and 140, electric charges may beaccumulated between the first and second internal electrodes 121 and122.

In this case, electrostatic capacity of the multilayered capacitor 100may be proportional to overlapped area of the first and second internalelectrodes 121 and 122, which overlap each other in the active region inthe Z direction.

Materials for forming the first and second internal electrodes 121 and122 are not particularly limited, and may be formed using a noble metalmaterial such as platinum (Pt), palladium (Pd), and palladium-silver(Pd—Ag) alloy, and the like, and a conductive paste made of one or morematerials of nickel (Ni) and copper (Cu).

In this case, a method of printing the conductive paste may use a screenprinting method, a gravure printing method, or the like, but the presentdisclosure is not limited thereto.

The first and second external electrodes 130 and 140 may be provided atvoltages of different polarities, may be disposed on both end portionsof the capacitor body 110 in the X direction, and may be in contact withand may be electrically connected to each of exposed portions of thefirst and second internal electrodes 121 and 122, respectively.

The first and second external electrodes 130 and 140 may include firstand second conductive layers 131 and 141 formed on the capacitor body110 to be connected to the first and second internal electrodes 121 and122; first and second inner plated layers 132 and 142 formed to coverthe first and second conductive layers 131 and 141, respectively; andfirst and second outer plated layers 133 and 143 formed to cover theinner plated layer, respectively.

The first conductive layer 131 may include a first connection portion131 a and a first bent portion 131 b.

The first connection portion 131 a may be formed on the third surface 3of the capacitor body 110, and may be connected to an exposed portion ofthe first internal electrode 121. The first bent portion 131 b may be aportion extending from the first connection portion 131 a to a portionof the first surface 1 of the capacitor body 110.

In this case, the first bent portion 131 b may further extend to aportion of the fifth and sixth surfaces 5 and 6, and a portion of thesecond surface 2 in the capacitor body 110, to improve fixationstrength, and the like.

The second conductive layer 141 may include a second connection portion141 a and a second bent portion 141 b.

The second connection portion 141 a may be formed on the fourth surface4 of the capacitor body 110, and may be connected to an exposed portionof the second internal electrode 122. The second bent portion 141 b maybe a portion extending from the second connection portion 141 a to aportion of the first surface 1 of the capacitor body 110.

In this case, the second bent portion 141 b may further extend to aportion of the fifth and sixth surfaces 5 and 6, and a portion of thesecond surface 2 in the capacitor body 110, to improve fixationstrength, and the like.

The first and second conductive layers 131 and 141 may include at leastone of copper (Cu) and silver (Ag), and may further include a glass, anepoxy, and the like, in addition thereto.

The first and second inner plated layers 132 and 142 may be includenickel (Ni) and phosphorus (P). For example, the first and second innerplated layers 132 and 142 may mainly contains nickel (Ni) and alsoinclude phosphorus (P) as an impurity dispersed in the first and secondinner plated layers 132 and 142. For another example, the first andsecond inner plated layers 132 and 142 may be plated nickel (Ni) layerswith phosphorus (P) as an impurity dispersed therein.

The first and second inner plated layers 132 and 142 may be formed byplating a first metal layer including nickel and phosphorus, on thefirst and second conductive layers 131 and 141.

In this case, the first and second inner plated layers 132 and 142 maybe formed by an electroless plating process, respectively. When thefirst and second inner plated layers 132 and 142 are formed by theelectroless plating process, the formed first and second inner platedlayers 132 and 142 may have better corrosion resistance, and may begenerally carried out the plating process evenly at every position tohave a uniform plating thickness, relative to the coated film formed byan electrolytic plating process, without having any difference inplating characteristics relative to those formed by the electrolyticplating process.

In addition, in the electrolytic plating process, a dummy such as asteel ball or the like may be further added to electrically conduct in abarrel plating operation. As in the present embodiment, when theelectroless plating process is performed, only a plated body may beplated without any dummy. Therefore, a plating preparation operation anda defect selection operation of a plated body after a plating operationmay be performed more easily.

The content of phosphorus in the first and second inner plated layers132 and 142 may be more than 4% by weight and 8% by weight or less,based on the total weight of the first and second inner plated layers132 and 142, respectively.

In the following Table 1, corrosion resistance may be confirmed by asalt spray test, and it can be confirmed that the longer the time, thebetter the corrosion resistance.

TABLE 1 Content of P Corrosion Max. Plating # (wt %) Resistance Rate(μm/hr) 1 0 2 3 24 hr 20 3 4 24 hr 20 4 5 96 hr 25 5 6 96 hr 25 6 7 96hr 25 7 8 96 hr 25 8 11 1000 hr  15 9 12 1000 hr  15

In this case, phosphorus may play a role of determining characteristicsof nickel coating. Referring to Table 1, #1, not including phosphorus(P), may be a condition that plating is not possible in the electrolessplating process.

It can be confirmed that the corrosion resistance of the first andsecond inner plated layers 132 and 142 were reduced in the cases of #2and #3 in which the content of phosphorus was 4 wt % or less.

It can be confirmed that precipitation rate of nickel was lowered in thecases of #8 and #9 in which the phosphorus content exceeds 8 wt %.

When the precipitation rate of nickel was lowered, the plating timebecomes longer to form the same plating thickness. Therefore,manufacturing time of a product increased to reduce productivitythereof.

Thicknesses of the first and second inner plated layers 132 and 142 maybe 1 μm or more and 10 μm or less. When the thicknesses of the first andsecond inner plated layers 132 and 142 are less than 1 μm, there may beproblems that nickel coverage is insufficient, and the first and secondconductive layers 131 and 141 are exposed. When the thicknesses of thefirst and second inner plated layers 132 and 142 are more than 10 μm,excessive plating time may be required.

The first and second outer plated layers 133 and 143 may includepalladium (Pd) and phosphorus (P). The content of phosphorus in thefirst and second outer plated layers 133 and 143 may be 2% by weight ormore and 6% by weight or less, based on the total weight of the firstand second outer plated layers 133 and 143, respectively. For example,the first and second outer plated layers 133 and 143 may mainly containpalladium (Pd) and also include phosphorus (P) as an impurity dispersedin the first and second outer plated layers 133 and 143. For anotherexample, the first and second outer plated layers 133 and 143 may beplated palladium (Pd) layers with phosphorus (P) as an impuritydispersed therein.

The first and second outer plated layers 133 and 143 may be formed byplating a second metal layer containing palladium and phosphorus on thefirst and second inner plated layers 132 and 142 respectively by theelectroless plating process.

Since the first and second outer plated layers 133 and 143 serve toprevent the nickel components in the first and second inner platedlayers 132 and 142 from being oxidized, the first and second outerplated layers 133 and 143 may be preferably formed thin by using amaterial including a noble metal with relatively low oxidation, ascompared to nickel.

For example, the thicknesses of the first and second outer plated layers133 and 143 may be less than the thickness of the first and second innerplated layers 132 and 142, respectively. When the thicknesses of thefirst and second outer plated layers 133 and 143 increase, there is ahigh possibility that problems such as breakage of the plated layer, andthe like, may occur.

When the first and second outer plated layers 133 and 143 are formed bythe electroless plating process, the formed first and second outerplated layers 133 and 143 may have better corrosion resistance, and maybe generally carried out the plating process evenly at every position tohave a uniform plating thickness, relative to the coated film formed byan electrolytic plating process, without having any difference inplating characteristics relative to those formed by the electrolyticplating process.

A multilayered capacitor of this embodiment may be a product which ismounted on a substrate by using a conductive adhesive and which areliability at a temperature of 150° C. or higher is required.

The first and second outer plated layers 133 and 143 may be portions ofthe substrate that may be in contact with the conductive adhesive whenthey are mounted on the substrate, may not deteriorate bonding forcewith the substrate, and may have no reliability problem at hightemperature, due to no tin contained.

According to an embodiment of the present disclosure, a decrease inbonding force between a conductive adhesive and a plated layer may beprevented to prevent a mounting failure of a multilayered capacitor,even when high reliability is required in a case in which themultilayered capacitor is mounted on a substrate using a conductiveadhesive.

While example embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentdisclosure as defined by the appended claims.

What is claimed is:
 1. A multilayered capacitor comprising: a capacitorbody including a plurality of dielectric layers and a plurality ofinternal electrodes; and external electrodes disposed on both endportions of the capacitor body and connected to exposed portions of theinternal electrodes, respectively, wherein each of the externalelectrodes includes: a conductive layer disposed on the capacitor bodyand connected to the internal electrodes; an inner plated layerincluding nickel (Ni) and phosphorus (P), and covering the conductivelayer; and an outer plated layer including palladium (Pd) and phosphorus(P), and covering the inner plated layer.
 2. The multilayered capacitoraccording to claim 1, wherein the inner plated layer has a phosphoruscontent of more than 4% by weight and 8% by weight or less, based on atotal weight of the inner plated layer.
 3. The multilayered capacitoraccording to claim 2, wherein the inner plated layer mainly containsnickel (Ni) and includes phosphorus (P) as an impurity dispersed in theinner plated layer.
 4. The multilayered capacitor according to claim 1,wherein the capacitor body comprises first and second surfaces facingeach other, third and fourth surfaces connected to the first and secondsurfaces and facing each other, and fifth and sixth surfaces connectedto the first and second surfaces and connected to the third and fourthsurfaces, and comprises the plurality of internal electrodes alternatelyexposed through the third and fourth surfaces of the capacitor body withthe dielectric layer interposed therebetween.
 5. The multilayeredcapacitor according to claim 4, wherein the conductive layers of theexternal electrodes comprise connection portions respectively disposedon the third and fourth surfaces of the capacitor body and connected tothe exposed portions of the internal electrodes, and bent portionsextending from the connection portions to a portion of the first surfaceof the capacitor body.
 6. The multilayered capacitor according to claim1, wherein the inner plated layer is formed by plating a first metallayer including nickel and phosphorus on the conductive layer by anelectroless plating process, and the outer plated layer is formed byplating a second metal layer including palladium and phosphorus on theinner plated layer by an electroless plating process.
 7. Themultilayered capacitor according to claim 1, wherein the conductivelayer comprises at least one of copper and silver.
 8. The multilayeredcapacitor according to claim 1, wherein the inner plated layer has athickness of 1 μm to 10 μm.
 9. The multilayered capacitor according toclaim 1, wherein a thickness of the inner plated layer is greater than athickness of the outer plated layer.
 10. The multilayered capacitoraccording to claim 1, wherein the outer plated layer has a phosphoruscontent of 2% by weight or more and 6% by weight or less, based on atotal weight of the outer plated layer.
 11. The multilayered capacitoraccording to claim 10, wherein the outer plated layer mainly containspalladium (Ni) and includes phosphorus (P) as an impurity dispersed inthe outer plated layer.
 12. The multilayered capacitor according toclaim 1, wherein each of the external electrodes does not contain a tin(Sn) layer.
 13. The multilayered capacitor according to claim 1, whereinthe outer plated layer is an outermost layer of each of the externalelectrodes.
 14. A multilayered capacitor comprising: a capacitor bodyincluding a plurality of dielectric layers and a plurality of internalelectrodes; and external electrodes disposed on both end portions of thecapacitor body and connected to exposed portions of the internalelectrodes, respectively, wherein each of the external electrodesincludes: a conductive layer disposed on the capacitor body andconnected to the internal electrodes; an inner nickel (Ni) layer withphosphorus (P) dispersed therein as an impurity, and covering theconductive layer; and an outer noble metal layer with phosphorus (P)dispersed therein as an impurity and covering layer the conductivelayer.
 15. The multilayered capacitor according to claim 14, wherein theouter noble metal layer is a palladium (Pd) layer with phosphorus (P)dispersed therein as the impurity.
 16. The multilayered capacitoraccording to claim 14, wherein the inner nickel (Ni) layer has aphosphorus content of more than 4% by weight and 8% by weight or less,based on a total weight of the inner nickel layer.
 17. The multilayeredcapacitor according to claim 14, wherein the outer noble metal layer hasa phosphorus content of 2% by weight or more and 6% by weight or less,based on a total weight of the outer noble metal layer.
 18. Themultilayered capacitor according to claim 14, wherein a thickness of theinner nickel (Ni) layer is greater than a thickness of the outer noblemetal layer.
 19. The multilayered capacitor according to claim 14,wherein each of the external electrodes does not contain a tin (Sn)layer.
 20. The multilayered capacitor according to claim 14, wherein theouter noble metal layer is an outermost layer of each of the externalelectrodes.